// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/kernel/power/snapshot.c
 *
 * This file provides system snapshot/restore functionality for swsusp.
 *
 * Copyright (C) 1998-2005 Pavel Machek <pavel@ucw.cz>
 * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
 */

#define pr_fmt(fmt) "PM: hibernation: " fmt

#include <linux/version.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/suspend.h>
#include <linux/delay.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/kernel.h>
#include <linux/pm.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/memblock.h>
#include <linux/nmi.h>
#include <linux/syscalls.h>
#include <linux/console.h>
#include <linux/highmem.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/compiler.h>
#include <linux/ktime.h>
#include <linux/set_memory.h>

#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/io.h>

#include "power.h"

#define SNAPSHOT_TWO 2
#define SNAPSHOT_FIVE 5

#if defined(CONFIG_STRICT_KERNEL_RWX) && defined(CONFIG_ARCH_HAS_SET_MEMORY)
static bool hibernate_restore_protection;
static bool hibernate_restore_protection_active;

void enable_restore_image_protection(void)
{
    hibernate_restore_protection = true;
}

static inline void hibernate_restore_protection_begin(void)
{
    hibernate_restore_protection_active = hibernate_restore_protection;
}

static inline void hibernate_restore_protection_end(void)
{
    hibernate_restore_protection_active = false;
}

static inline void hibernate_restore_protect_page(void *page_address)
{
    if (hibernate_restore_protection_active) {
        set_memory_ro((unsigned long)page_address, 1);
    }
}

static inline void hibernate_restore_unprotect_page(void *page_address)
{
    if (hibernate_restore_protection_active) {
        set_memory_rw((unsigned long)page_address, 1);
    }
}
#else
static inline void hibernate_restore_protection_begin(void)
{
}
static inline void hibernate_restore_protection_end(void)
{
}
static inline void hibernate_restore_protect_page(void *page_address)
{
}
static inline void hibernate_restore_unprotect_page(void *page_address)
{
}
#endif /* CONFIG_STRICT_KERNEL_RWX  && CONFIG_ARCH_HAS_SET_MEMORY */

static int swsusp_page_is_free(struct page *);
static void swsusp_set_page_forbidden(struct page *);
static void swsusp_unset_page_forbidden(struct page *);

/*
 * Number of bytes to reserve for memory allocations made by device drivers
 * from their ->freeze() and ->freeze_noirq() callbacks so that they don't
 * cause image creation to fail (tunable via /sys/power/reserved_size).
 */
unsigned long reserved_size;

void __init hibernate_reserved_size_init(void)
{
    reserved_size = SPARE_PAGES * PAGE_SIZE;
}

/*
 * Preferred image size in bytes (tunable via /sys/power/image_size).
 * When it is set to N, swsusp will do its best to ensure the image
 * size will not exceed N bytes, but if that is impossible, it will
 * try to create the smallest image possible.
 */
unsigned long image_size;

void __init hibernate_image_size_init(void)
{
    image_size = ((totalram_pages() * SNAPSHOT_TWO) / SNAPSHOT_FIVE) * PAGE_SIZE;
}

/*
 * List of PBEs needed for restoring the pages that were allocated before
 * the suspend and included in the suspend image, but have also been
 * allocated by the "resume" kernel, so their contents cannot be written
 * directly to their "original" page frames.
 */
struct pbe *restore_pblist;

/* struct linked_page is used to build chains of pages */

#define LINKED_PAGE_DATA_SIZE (PAGE_SIZE - sizeof(void *))

struct linked_page {
    struct linked_page *next;
    char data[LINKED_PAGE_DATA_SIZE];
} __packed;

/*
 * List of "safe" pages (ie. pages that were not used by the image kernel
 * before hibernation) that may be used as temporary storage for image kernel
 * memory contents.
 */
static struct linked_page *safe_pages_list;

/* Pointer to an auxiliary buffer (1 page) */
static void *buffer;

#define PG_ANY 0
#define PG_SAFE 1
#define PG_UNSAFE_CLEAR 1
#define PG_UNSAFE_KEEP 0

static unsigned int allocated_unsafe_pages;

/**
 * get_image_page - Allocate a page for a hibernation image.
 * @gfp_mask: GFP mask for the allocation.
 * @safe_needed: Get pages that were not used before hibernation (restore only)
 *
 * During image restoration, for storing the PBE list and the image data, we can
 * only use memory pages that do not conflict with the pages used before
 * hibernation.  The "unsafe" pages have PageNosaveFree set and we count them
 * using allocated_unsafe_pages.
 *
 * Each allocated image page is marked as PageNosave and PageNosaveFree so that
 * swsusp_free() can release it.
 */
static void *get_image_page(gfp_t gfp_mask, int safe_needed)
{
    void *res;

    res = (void *)get_zeroed_page(gfp_mask);
    if (safe_needed) {
        while (res && swsusp_page_is_free(virt_to_page(res))) {
            /* The page is unsafe, mark it for swsusp_free() */
            swsusp_set_page_forbidden(virt_to_page(res));
            allocated_unsafe_pages++;
            res = (void *)get_zeroed_page(gfp_mask);
        }
    }
    if (res) {
        swsusp_set_page_forbidden(virt_to_page(res));
        swsusp_set_page_free(virt_to_page(res));
    }
    return res;
}

static void *_get_safe_page(gfp_t gfp_mask)
{
    if (safe_pages_list) {
        void *ret = safe_pages_list;

        safe_pages_list = safe_pages_list->next;
        memset(ret, 0, PAGE_SIZE);
        return ret;
    }
    return get_image_page(gfp_mask, PG_SAFE);
}

unsigned long get_safe_page(gfp_t gfp_mask)
{
    return (unsigned long)_get_safe_page(gfp_mask);
}

static struct page *alloc_image_page(gfp_t gfp_mask)
{
    struct page *page;

    page = alloc_page(gfp_mask);
    if (page) {
        swsusp_set_page_forbidden(page);
        swsusp_set_page_free(page);
    }
    return page;
}

static void recycle_safe_page(void *page_address)
{
    struct linked_page *lp = page_address;

    lp->next = safe_pages_list;
    safe_pages_list = lp;
}

/**
 * free_image_page - Free a page allocated for hibernation image.
 * @addr: Address of the page to free.
 * @clear_nosave_free: If set, clear the PageNosaveFree bit for the page.
 *
 * The page to free should have been allocated by get_image_page() (page flags
 * set by it are affected).
 */
static inline void free_image_page(void *addr, int clear_nosave_free)
{
    struct page *page;

    BUG_ON(!virt_addr_valid(addr));

    page = virt_to_page(addr);

    swsusp_unset_page_forbidden(page);
    if (clear_nosave_free) {
        swsusp_unset_page_free(page);
    }

    __free_page(page);
}

static inline void free_list_of_pages(struct linked_page *list, int clear_page_nosave)
{
    while (list) {
        struct linked_page *lp = list->next;

        free_image_page(list, clear_page_nosave);
        list = lp;
    }
}

/*
 * struct chain_allocator is used for allocating small objects out of
 * a linked list of pages called 'the chain'.
 *
 * The chain grows each time when there is no room for a new object in
 * the current page.  The allocated objects cannot be freed individually.
 * It is only possible to free them all at once, by freeing the entire
 * chain.
 *
 * NOTE: The chain allocator may be inefficient if the allocated objects
 * are not much smaller than PAGE_SIZE.
 */
struct chain_allocator {
    struct linked_page *chain; /* the chain */
    unsigned int used_space;   /* total size of objects allocated out
                      of the current page */
    gfp_t gfp_mask;            /* mask for allocating pages */
    int safe_needed;           /* if set, only "safe" pages are allocated */
};

static void chain_init(struct chain_allocator *ca, gfp_t gfp_mask, int safe_needed)
{
    ca->chain = NULL;
    ca->used_space = LINKED_PAGE_DATA_SIZE;
    ca->gfp_mask = gfp_mask;
    ca->safe_needed = safe_needed;
}

static void *chain_alloc(struct chain_allocator *ca, unsigned int size)
{
    void *ret;

    if (LINKED_PAGE_DATA_SIZE - ca->used_space < size) {
        struct linked_page *lp;

        lp = ca->safe_needed ? _get_safe_page(ca->gfp_mask) : get_image_page(ca->gfp_mask, PG_ANY);
        if (!lp) {
            return NULL;
        }

        lp->next = ca->chain;
        ca->chain = lp;
        ca->used_space = 0;
    }
    ret = ca->chain->data + ca->used_space;
    ca->used_space += size;
    return ret;
}

/**
 * Data types related to memory bitmaps.
 *
 * Memory bitmap is a structure consiting of many linked lists of
 * objects.  The main list's elements are of type struct zone_bitmap
 * and each of them corresonds to one zone.  For each zone bitmap
 * object there is a list of objects of type struct bm_block that
 * represent each blocks of bitmap in which information is stored.
 *
 * struct memory_bitmap contains a pointer to the main list of zone
 * bitmap objects, a struct bm_position used for browsing the bitmap,
 * and a pointer to the list of pages used for allocating all of the
 * zone bitmap objects and bitmap block objects.
 *
 * NOTE: It has to be possible to lay out the bitmap in memory
 * using only allocations of order 0.  Additionally, the bitmap is
 * designed to work with arbitrary number of zones (this is over the
 * top for now, but let's avoid making unnecessary assumptions ;-).
 *
 * struct zone_bitmap contains a pointer to a list of bitmap block
 * objects and a pointer to the bitmap block object that has been
 * most recently used for setting bits.  Additionally, it contains the
 * PFNs that correspond to the start and end of the represented zone.
 *
 * struct bm_block contains a pointer to the memory page in which
 * information is stored (in the form of a block of bitmap)
 * It also contains the pfns that correspond to the start and end of
 * the represented memory area.
 *
 * The memory bitmap is organized as a radix tree to guarantee fast random
 * access to the bits. There is one radix tree for each zone (as returned
 * from create_mem_extents).
 *
 * One radix tree is represented by one struct mem_zone_bm_rtree. There are
 * two linked lists for the nodes of the tree, one for the inner nodes and
 * one for the leave nodes. The linked leave nodes are used for fast linear
 * access of the memory bitmap.
 *
 * The struct rtree_node represents one node of the radix tree.
 */

#define BM_END_OF_MAP (~0UL)

#define BM_BITS_PER_BLOCK (PAGE_SIZE * BITS_PER_BYTE)
#define BM_BLOCK_SHIFT (PAGE_SHIFT + 3)
#define BM_BLOCK_MASK ((1UL << BM_BLOCK_SHIFT) - 1)

/*
 * struct rtree_node is a wrapper struct to link the nodes
 * of the rtree together for easy linear iteration over
 * bits and easy freeing
 */
struct rtree_node {
    struct list_head list;
    unsigned long *data;
};

/*
 * struct mem_zone_bm_rtree represents a bitmap used for one
 * populated memory zone.
 */
struct mem_zone_bm_rtree {
    struct list_head list;    /* Link Zones together         */
    struct list_head nodes;   /* Radix Tree inner nodes      */
    struct list_head leaves;  /* Radix Tree leaves           */
    unsigned long start_pfn;  /* Zone start page frame       */
    unsigned long end_pfn;    /* Zone end page frame + 1     */
    struct rtree_node *rtree; /* Radix Tree Root             */
    int levels;               /* Number of Radix Tree Levels */
    unsigned int blocks;      /* Number of Bitmap Blocks     */
};

/* strcut bm_position is used for browsing memory bitmaps */

struct bm_position {
    struct mem_zone_bm_rtree *zone;
    struct rtree_node *node;
    unsigned long node_pfn;
    int node_bit;
};

struct memory_bitmap {
    struct list_head zones;
    struct linked_page *p_list; /* list of pages used to store zone
                    bitmap objects and bitmap block
                    objects */
    struct bm_position cur;     /* most recently used bit position */
};

/* Functions that operate on memory bitmaps */

#define BM_ENTRIES_PER_LEVEL (PAGE_SIZE / sizeof(unsigned long))
#if BITS_PER_LONG == 32
#define BM_RTREE_LEVEL_SHIFT (PAGE_SHIFT - 2)
#else
#define BM_RTREE_LEVEL_SHIFT (PAGE_SHIFT - 3)
#endif
#define BM_RTREE_LEVEL_MASK ((1UL << BM_RTREE_LEVEL_SHIFT) - 1)

/**
 * alloc_rtree_node - Allocate a new node and add it to the radix tree.
 *
 * This function is used to allocate inner nodes as well as the
 * leave nodes of the radix tree. It also adds the node to the
 * corresponding linked list passed in by the *list parameter.
 */
static struct rtree_node *alloc_rtree_node(gfp_t gfp_mask, int safe_needed, struct chain_allocator *ca,
                                           struct list_head *list)
{
    struct rtree_node *node;

    node = chain_alloc(ca, sizeof(struct rtree_node));
    if (!node) {
        return NULL;
    }

    node->data = get_image_page(gfp_mask, safe_needed);
    if (!node->data) {
        return NULL;
    }

    list_add_tail(&node->list, list);

    return node;
}

/**
 * add_rtree_block - Add a new leave node to the radix tree.
 *
 * The leave nodes need to be allocated in order to keep the leaves
 * linked list in order. This is guaranteed by the zone->blocks
 * counter.
 */
static int add_rtree_block(struct mem_zone_bm_rtree *zone, gfp_t gfp_mask, int safe_needed, struct chain_allocator *ca)
{
    struct rtree_node *node, *block, **dst;
    unsigned int levels_needed, block_nr;
    int i;

    block_nr = zone->blocks;
    levels_needed = 0;

    /* How many levels do we need for this block nr? */
    while (block_nr) {
        levels_needed += 1;
        block_nr >>= BM_RTREE_LEVEL_SHIFT;
    }

    /* Make sure the rtree has enough levels */
    for (i = zone->levels; i < levels_needed; i++) {
        node = alloc_rtree_node(gfp_mask, safe_needed, ca, &zone->nodes);
        if (!node) {
            return -ENOMEM;
        }

        node->data[0] = (unsigned long)zone->rtree;
        zone->rtree = node;
        zone->levels += 1;
    }

    /* Allocate new block */
    block = alloc_rtree_node(gfp_mask, safe_needed, ca, &zone->leaves);
    if (!block) {
        return -ENOMEM;
    }

    /* Now walk the rtree to insert the block */
    node = zone->rtree;
    dst = &zone->rtree;
    block_nr = zone->blocks;
    for (i = zone->levels; i > 0; i--) {
        int index;

        if (!node) {
            node = alloc_rtree_node(gfp_mask, safe_needed, ca, &zone->nodes);
            if (!node) {
                return -ENOMEM;
            }
            *dst = node;
        }

        index = block_nr >> ((i - 1) * BM_RTREE_LEVEL_SHIFT);
        index &= BM_RTREE_LEVEL_MASK;
        dst = (struct rtree_node **)&((*dst)->data[index]);
        node = *dst;
    }

    zone->blocks += 1;
    *dst = block;

    return 0;
}

static void free_zone_bm_rtree(struct mem_zone_bm_rtree *zone, int clear_nosave_free);

/**
 * create_zone_bm_rtree - Create a radix tree for one zone.
 *
 * Allocated the mem_zone_bm_rtree structure and initializes it.
 * This function also allocated and builds the radix tree for the
 * zone.
 */
static struct mem_zone_bm_rtree *create_zone_bm_rtree(gfp_t gfp_mask, int safe_needed, struct chain_allocator *ca,
                                                      unsigned long start, unsigned long end)
{
    struct mem_zone_bm_rtree *zone;
    unsigned int i, nr_blocks;
    unsigned long pages;

    pages = end - start;
    zone = chain_alloc(ca, sizeof(struct mem_zone_bm_rtree));
    if (!zone) {
        return NULL;
    }

    INIT_LIST_HEAD(&zone->nodes);
    INIT_LIST_HEAD(&zone->leaves);
    zone->start_pfn = start;
    zone->end_pfn = end;
    nr_blocks = DIV_ROUND_UP(pages, BM_BITS_PER_BLOCK);

    for (i = 0; i < nr_blocks; i++) {
        if (add_rtree_block(zone, gfp_mask, safe_needed, ca)) {
            free_zone_bm_rtree(zone, PG_UNSAFE_CLEAR);
            return NULL;
        }
    }

    return zone;
}

/**
 * free_zone_bm_rtree - Free the memory of the radix tree.
 *
 * Free all node pages of the radix tree. The mem_zone_bm_rtree
 * structure itself is not freed here nor are the rtree_node
 * structs.
 */
static void free_zone_bm_rtree(struct mem_zone_bm_rtree *zone, int clear_nosave_free)
{
    struct rtree_node *node;

    list_for_each_entry(node, &zone->nodes, list) free_image_page(node->data, clear_nosave_free);

    list_for_each_entry(node, &zone->leaves, list) free_image_page(node->data, clear_nosave_free);
}

static void memory_bm_position_reset(struct memory_bitmap *bm)
{
    bm->cur.zone = list_entry(bm->zones.next, struct mem_zone_bm_rtree, list);
    bm->cur.node = list_entry(bm->cur.zone->leaves.next, struct rtree_node, list);
    bm->cur.node_pfn = 0;
    bm->cur.node_bit = 0;
}

static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free);

struct mem_extent {
    struct list_head hook;
    unsigned long start;
    unsigned long end;
};

/**
 * free_mem_extents - Free a list of memory extents.
 * @list: List of extents to free.
 */
static void free_mem_extents(struct list_head *list)
{
    struct mem_extent *ext, *aux;

    list_for_each_entry_safe(ext, aux, list, hook)
    {
        list_del(&ext->hook);
        kfree(ext);
    }
}

/**
 * create_mem_extents - Create a list of memory extents.
 * @list: List to put the extents into.
 * @gfp_mask: Mask to use for memory allocations.
 *
 * The extents represent contiguous ranges of PFNs.
 */
static int create_mem_extents(struct list_head *list, gfp_t gfp_mask)
{
    struct zone *zone;

    INIT_LIST_HEAD(list);

    for_each_populated_zone(zone)
    {
        unsigned long zone_start, zone_end;
        struct mem_extent *ext, *cur, *aux;

        zone_start = zone->zone_start_pfn;
        zone_end = zone_end_pfn(zone);

        list_for_each_entry(ext, list, hook) if (zone_start <= ext->end) break;

        if (&ext->hook == list || zone_end < ext->start) {
            /* New extent is necessary */
            struct mem_extent *new_ext;

            new_ext = kzalloc(sizeof(struct mem_extent), gfp_mask);
            if (!new_ext) {
                free_mem_extents(list);
                return -ENOMEM;
            }
            new_ext->start = zone_start;
            new_ext->end = zone_end;
            list_add_tail(&new_ext->hook, &ext->hook);
            continue;
        }

        /* Merge this zone's range of PFNs with the existing one */
        if (zone_start < ext->start) {
            ext->start = zone_start;
        }
        if (zone_end > ext->end) {
            ext->end = zone_end;
        }

        /* More merging may be possible */
        cur = ext;
        list_for_each_entry_safe_continue(cur, aux, list, hook)
        {
            if (zone_end < cur->start) {
                break;
            }
            if (zone_end < cur->end) {
                ext->end = cur->end;
            }
            list_del(&cur->hook);
            kfree(cur);
        }
    }

    return 0;
}

/**
 * memory_bm_create - Allocate memory for a memory bitmap.
 */
static int memory_bm_create(struct memory_bitmap *bm, gfp_t gfp_mask, int safe_needed)
{
    struct chain_allocator ca;
    struct list_head mem_extents;
    struct mem_extent *ext;
    int error;

    chain_init(&ca, gfp_mask, safe_needed);
    INIT_LIST_HEAD(&bm->zones);

    error = create_mem_extents(&mem_extents, gfp_mask);
    if (error) {
        return error;
    }

    list_for_each_entry(ext, &mem_extents, hook)
    {
        struct mem_zone_bm_rtree *zone;

        zone = create_zone_bm_rtree(gfp_mask, safe_needed, &ca, ext->start, ext->end);
        if (!zone) {
            error = -ENOMEM;
            goto Error;
        }
        list_add_tail(&zone->list, &bm->zones);
    }

    bm->p_list = ca.chain;
    memory_bm_position_reset(bm);
    while (1) {
        free_mem_extents(&mem_extents);
        return error;

    Error:
        bm->p_list = ca.chain;
        memory_bm_free(bm, PG_UNSAFE_CLEAR);
        continue;
    }
}

/**
 * memory_bm_free - Free memory occupied by the memory bitmap.
 * @bm: Memory bitmap.
 */
static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free)
{
    struct mem_zone_bm_rtree *zone;

    list_for_each_entry(zone, &bm->zones, list) free_zone_bm_rtree(zone, clear_nosave_free);

    free_list_of_pages(bm->p_list, clear_nosave_free);

    INIT_LIST_HEAD(&bm->zones);
}

/**
 * memory_bm_find_bit - Find the bit for a given PFN in a memory bitmap.
 *
 * Find the bit in memory bitmap @bm that corresponds to the given PFN.
 * The cur.zone, cur.block and cur.node_pfn members of @bm are updated.
 *
 * Walk the radix tree to find the page containing the bit that represents @pfn
 * and return the position of the bit in @addr and @bit_nr.
 */
static int memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn, void **addr, unsigned int *bit_nr)
{
    struct mem_zone_bm_rtree *curr, *zone;
    struct rtree_node *node;
    int i, block_nr;

    zone = bm->cur.zone;

    if (pfn >= zone->start_pfn && pfn < zone->end_pfn) {
        goto zone_found;
    }

    zone = NULL;

    /* Find the right zone */
    list_for_each_entry(curr, &bm->zones, list)
    {
        if (pfn >= curr->start_pfn && pfn < curr->end_pfn) {
            zone = curr;
            break;
        }
    }

    if (!zone) {
        return -EFAULT;
    }

zone_found:
    /*
     * We have found the zone. Now walk the radix tree to find the leaf node
     * for our PFN.
     */

    /*
     * If the zone we wish to scan is the current zone and the
     * pfn falls into the current node then we do not need to walk
     * the tree.
     */
    node = bm->cur.node;
    if (zone == bm->cur.zone && ((pfn - zone->start_pfn) & ~BM_BLOCK_MASK) == bm->cur.node_pfn) {
        goto node_found;
    }

    node = zone->rtree;
    block_nr = (pfn - zone->start_pfn) >> BM_BLOCK_SHIFT;

    for (i = zone->levels; i > 0; i--) {
        int index;

        index = block_nr >> ((i - 1) * BM_RTREE_LEVEL_SHIFT);
        index &= BM_RTREE_LEVEL_MASK;
        BUG_ON(node->data[index] == 0);
        node = (struct rtree_node *)node->data[index];
    }

node_found:
    /* Update last position */
    bm->cur.zone = zone;
    bm->cur.node = node;
    bm->cur.node_pfn = (pfn - zone->start_pfn) & ~BM_BLOCK_MASK;

    /* Set return values */
    *addr = node->data;
    *bit_nr = (pfn - zone->start_pfn) & BM_BLOCK_MASK;

    return 0;
}

static void memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
{
    void *addr;
    unsigned int bit;
    int error;

    error = memory_bm_find_bit(bm, pfn, &addr, &bit);
    BUG_ON(error);
    set_bit(bit, addr);
}

static int mem_bm_set_bit_check(struct memory_bitmap *bm, unsigned long pfn)
{
    void *addr;
    unsigned int bit;
    int error;

    error = memory_bm_find_bit(bm, pfn, &addr, &bit);
    if (!error) {
        set_bit(bit, addr);
    }

    return error;
}

static void memory_bm_clear_bit(struct memory_bitmap *bm, unsigned long pfn)
{
    void *addr;
    unsigned int bit;
    int error;

    error = memory_bm_find_bit(bm, pfn, &addr, &bit);
    BUG_ON(error);
    clear_bit(bit, addr);
}

static void memory_bm_clear_current(struct memory_bitmap *bm)
{
    int bit;

    bit = max(bm->cur.node_bit - 1, 0);
    clear_bit(bit, bm->cur.node->data);
}

static int memory_bm_test_bit(struct memory_bitmap *bm, unsigned long pfn)
{
    void *addr;
    unsigned int bit;
    int error;

    error = memory_bm_find_bit(bm, pfn, &addr, &bit);
    BUG_ON(error);
    return test_bit(bit, addr);
}

static bool memory_bm_pfn_present(struct memory_bitmap *bm, unsigned long pfn)
{
    void *addr;
    unsigned int bit;

    return !memory_bm_find_bit(bm, pfn, &addr, &bit);
}

/*
 * rtree_next_node - Jump to the next leaf node.
 *
 * Set the position to the beginning of the next node in the
 * memory bitmap. This is either the next node in the current
 * zone's radix tree or the first node in the radix tree of the
 * next zone.
 *
 * Return true if there is a next node, false otherwise.
 */
static bool rtree_next_node(struct memory_bitmap *bm)
{
    if (!list_is_last(&bm->cur.node->list, &bm->cur.zone->leaves)) {
        bm->cur.node = list_entry(bm->cur.node->list.next, struct rtree_node, list);
        bm->cur.node_pfn += BM_BITS_PER_BLOCK;
        bm->cur.node_bit = 0;
        touch_softlockup_watchdog();
        return true;
    }

    /* No more nodes, goto next zone */
    if (!list_is_last(&bm->cur.zone->list, &bm->zones)) {
        bm->cur.zone = list_entry(bm->cur.zone->list.next, struct mem_zone_bm_rtree, list);
        bm->cur.node = list_entry(bm->cur.zone->leaves.next, struct rtree_node, list);
        bm->cur.node_pfn = 0;
        bm->cur.node_bit = 0;
        return true;
    }

    /* No more zones */
    return false;
}

/**
 * memory_bm_rtree_next_pfn - Find the next set bit in a memory bitmap.
 * @bm: Memory bitmap.
 *
 * Starting from the last returned position this function searches for the next
 * set bit in @bm and returns the PFN represented by it.  If no more bits are
 * set, BM_END_OF_MAP is returned.
 *
 * It is required to run memory_bm_position_reset() before the first call to
 * this function for the given memory bitmap.
 */
static unsigned long memory_bm_next_pfn(struct memory_bitmap *bm)
{
    unsigned long bits, pfn, pages;
    int bit;

    do {
        pages = bm->cur.zone->end_pfn - bm->cur.zone->start_pfn;
        bits = min(pages - bm->cur.node_pfn, BM_BITS_PER_BLOCK);
        bit = find_next_bit(bm->cur.node->data, bits, bm->cur.node_bit);
        if (bit < bits) {
            pfn = bm->cur.zone->start_pfn + bm->cur.node_pfn + bit;
            bm->cur.node_bit = bit + 1;
            return pfn;
        }
    } while (rtree_next_node(bm));

    return BM_END_OF_MAP;
}

/*
 * This structure represents a range of page frames the contents of which
 * should not be saved during hibernation.
 */
struct nosave_region {
    struct list_head list;
    unsigned long start_pfn;
    unsigned long end_pfn;
};

static LIST_HEAD(nosave_regions);

static void recycle_zone_bm_rtree(struct mem_zone_bm_rtree *zone)
{
    struct rtree_node *node;

    list_for_each_entry(node, &zone->nodes, list) recycle_safe_page(node->data);

    list_for_each_entry(node, &zone->leaves, list) recycle_safe_page(node->data);
}

static void memory_bm_recycle(struct memory_bitmap *bm)
{
    struct mem_zone_bm_rtree *zone;
    struct linked_page *p_list;

    list_for_each_entry(zone, &bm->zones, list) recycle_zone_bm_rtree(zone);

    p_list = bm->p_list;
    while (p_list) {
        struct linked_page *lp = p_list;

        p_list = lp->next;
        recycle_safe_page(lp);
    }
}

/**
 * register_nosave_region - Register a region of unsaveable memory.
 *
 * Register a range of page frames the contents of which should not be saved
 * during hibernation (to be used in the early initialization code).
 */
void __init register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
{
    struct nosave_region *region;

    if (start_pfn >= end_pfn) {
        return;
    }

    if (!list_empty(&nosave_regions)) {
        /* Try to extend the previous region (they should be sorted) */
        region = list_entry(nosave_regions.prev,
                    struct nosave_region, list);
        if (region->end_pfn == start_pfn) {
            region->end_pfn = end_pfn;
            goto Report;
        }
    }
    /* This allocation cannot fail */
    region = memblock_alloc(sizeof(struct nosave_region),
                SMP_CACHE_BYTES);
    if (!region)
        panic("%s: Failed to allocate %zu bytes\n", __func__,
              sizeof(struct nosave_region));
    region->start_pfn = start_pfn;
    region->end_pfn = end_pfn;
    list_add_tail(&region->list, &nosave_regions);
 Report:
    pr_info("Registered nosave memory: [mem %#010llx-%#010llx]\n",
        (unsigned long long) start_pfn << PAGE_SHIFT,
        ((unsigned long long) end_pfn << PAGE_SHIFT) - 1);
}

/*
 * Set bits in this map correspond to the page frames the contents of which
 * should not be saved during the suspend.
 */
static struct memory_bitmap *forbidden_pages_map;

/* Set bits in this map correspond to free page frames. */
static struct memory_bitmap *free_pages_map;

/*
 * Each page frame allocated for creating the image is marked by setting the
 * corresponding bits in forbidden_pages_map and free_pages_map simultaneously
 */

void swsusp_set_page_free(struct page *page)
{
    if (free_pages_map) {
        memory_bm_set_bit(free_pages_map, page_to_pfn(page));
    }
}

static int swsusp_page_is_free(struct page *page)
{
    return free_pages_map ? memory_bm_test_bit(free_pages_map, page_to_pfn(page)) : 0;
}

void swsusp_unset_page_free(struct page *page)
{
    if (free_pages_map) {
        memory_bm_clear_bit(free_pages_map, page_to_pfn(page));
    }
}

static void swsusp_set_page_forbidden(struct page *page)
{
    if (forbidden_pages_map) {
        memory_bm_set_bit(forbidden_pages_map, page_to_pfn(page));
    }
}

int swsusp_page_is_forbidden(struct page *page)
{
    return forbidden_pages_map ? memory_bm_test_bit(forbidden_pages_map, page_to_pfn(page)) : 0;
}

static void swsusp_unset_page_forbidden(struct page *page)
{
    if (forbidden_pages_map) {
        memory_bm_clear_bit(forbidden_pages_map, page_to_pfn(page));
    }
}

/**
 * mark_nosave_pages - Mark pages that should not be saved.
 * @bm: Memory bitmap.
 *
 * Set the bits in @bm that correspond to the page frames the contents of which
 * should not be saved.
 */
static void mark_nosave_pages(struct memory_bitmap *bm)
{
    struct nosave_region *region;

    if (list_empty(&nosave_regions)) {
        return;
    }

    list_for_each_entry(region, &nosave_regions, list)
    {
        unsigned long pfn;

        pr_debug("Marking nosave pages: [mem %#010llx-%#010llx]\n", (unsigned long long)region->start_pfn << PAGE_SHIFT,
                 ((unsigned long long)region->end_pfn << PAGE_SHIFT) - 1);

        for (pfn = region->start_pfn; pfn < region->end_pfn; pfn++) {
            if (pfn_valid(pfn)) {
                /*
                 * It is safe to ignore the result of
                 * mem_bm_set_bit_check() here, since we won't
                 * touch the PFNs for which the error is
                 * returned anyway.
                 */
                mem_bm_set_bit_check(bm, pfn);
            }
        }
    }
}

/**
 * create_basic_memory_bitmaps - Create bitmaps to hold basic page information.
 *
 * Create bitmaps needed for marking page frames that should not be saved and
 * free page frames.  The forbidden_pages_map and free_pages_map pointers are
 * only modified if everything goes well, because we don't want the bits to be
 * touched before both bitmaps are set up.
 */
int create_basic_memory_bitmaps(void)
{
    struct memory_bitmap *bm1, *bm2;
    int error = 0;

    if (forbidden_pages_map && free_pages_map) {
        return 0;
    } else {
        BUG_ON(forbidden_pages_map || free_pages_map);
    }

    bm1 = kzalloc(sizeof(struct memory_bitmap), GFP_KERNEL);
    if (!bm1) {
        return -ENOMEM;
    }

    error = memory_bm_create(bm1, GFP_KERNEL, PG_ANY);
    if (error) {
        goto Free_first_object;
    }

    bm2 = kzalloc(sizeof(struct memory_bitmap), GFP_KERNEL);
    if (!bm2) {
        goto Free_first_bitmap;
    }

    error = memory_bm_create(bm2, GFP_KERNEL, PG_ANY);
    if (error) {
        goto Free_second_object;
    }

    forbidden_pages_map = bm1;
    free_pages_map = bm2;
    mark_nosave_pages(forbidden_pages_map);

    pr_debug("Basic memory bitmaps created\n");

    return 0;

Free_second_object:
    kfree(bm2);
Free_first_bitmap:
    memory_bm_free(bm1, PG_UNSAFE_CLEAR);
Free_first_object:
    kfree(bm1);
    return -ENOMEM;
}

/**
 * free_basic_memory_bitmaps - Free memory bitmaps holding basic information.
 *
 * Free memory bitmaps allocated by create_basic_memory_bitmaps().  The
 * auxiliary pointers are necessary so that the bitmaps themselves are not
 * referred to while they are being freed.
 */
void free_basic_memory_bitmaps(void)
{
    struct memory_bitmap *bm1, *bm2;

    if (WARN_ON(!(forbidden_pages_map && free_pages_map))) {
        return;
    }

    bm1 = forbidden_pages_map;
    bm2 = free_pages_map;
    forbidden_pages_map = NULL;
    free_pages_map = NULL;
    memory_bm_free(bm1, PG_UNSAFE_CLEAR);
    kfree(bm1);
    memory_bm_free(bm2, PG_UNSAFE_CLEAR);
    kfree(bm2);

    pr_debug("Basic memory bitmaps freed\n");
}

static void clear_or_poison_free_page(struct page *page)
{
    if (page_poisoning_enabled_static()) {
        _kernel_poison_pages(page, 1);
    } else if (want_init_on_free()) {
        clear_highpage(page);
    }
}

void clear_or_poison_free_pages(void)
{
    struct memory_bitmap *bm = free_pages_map;
    unsigned long pfn;

    if (WARN_ON(!(free_pages_map))) {
        return;
    }

    if (page_poisoning_enabled() || want_init_on_free()) {
        memory_bm_position_reset(bm);
        pfn = memory_bm_next_pfn(bm);
        while (pfn != BM_END_OF_MAP) {
            if (pfn_valid(pfn)) {
                clear_or_poison_free_page(pfn_to_page(pfn));
            }

            pfn = memory_bm_next_pfn(bm);
        }
        memory_bm_position_reset(bm);
        pr_info("free pages cleared after restore\n");
    }
}

/**
 * snapshot_additional_pages - Estimate the number of extra pages needed.
 * @zone: Memory zone to carry out the computation for.
 *
 * Estimate the number of additional pages needed for setting up a hibernation
 * image data structures for @zone (usually, the returned value is greater than
 * the exact number).
 */
unsigned int snapshot_additional_pages(struct zone *zone)
{
    unsigned int rtree, nodes;

    rtree = nodes = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
    rtree += DIV_ROUND_UP(rtree * sizeof(struct rtree_node), LINKED_PAGE_DATA_SIZE);
    while (nodes > 1) {
        nodes = DIV_ROUND_UP(nodes, BM_ENTRIES_PER_LEVEL);
        rtree += nodes;
    }

    return 0x2 * rtree;
}

#ifdef CONFIG_HIGHMEM
/**
 * count_free_highmem_pages - Compute the total number of free highmem pages.
 *
 * The returned number is system-wide.
 */
static unsigned int count_free_highmem_pages(void)
{
    struct zone *zone;
    unsigned int cnt = 0;

    for_each_populated_zone(zone) if (is_highmem(zone)) cnt += zone_page_state(zone, NR_FREE_PAGES);

    return cnt;
}

/**
 * saveable_highmem_page - Check if a highmem page is saveable.
 *
 * Determine whether a highmem page should be included in a hibernation image.
 *
 * We should save the page if it isn't Nosave or NosaveFree, or Reserved,
 * and it isn't part of a free chunk of pages.
 */
static struct page *saveable_highmem_page(struct zone *zone, unsigned long pfn)
{
    struct page *page;

    if (!pfn_valid(pfn)) {
        return NULL;
    }

    page = pfn_to_online_page(pfn);
    if (!page || page_zone(page) != zone) {
        return NULL;
    }

    BUG_ON(!PageHighMem(page));

    if (swsusp_page_is_forbidden(page) || swsusp_page_is_free(page)) {
        return NULL;
    }

    if (PageReserved(page) || PageOffline(page)) {
        return NULL;
    }

    if (page_is_guard(page)) {
        return NULL;
    }

    return page;
}

/**
 * count_highmem_pages - Compute the total number of saveable highmem pages.
 */
static unsigned int count_highmem_pages(void)
{
    struct zone *zone;
    unsigned int n = 0;

    for_each_populated_zone(zone)
    {
        unsigned long pfn, max_zone_pfn;

        if (!is_highmem(zone)) {
            continue;
        }

        mark_free_pages(zone);
        max_zone_pfn = zone_end_pfn(zone);
        for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
            if (saveable_highmem_page(zone, pfn)) {
                n++;
            }
        }
    }
    return n;
}
#else
static inline void *saveable_highmem_page(struct zone *z, unsigned long p)
{
    return NULL;
}
#endif /* CONFIG_HIGHMEM */

/**
 * saveable_page - Check if the given page is saveable.
 *
 * Determine whether a non-highmem page should be included in a hibernation
 * image.
 *
 * We should save the page if it isn't Nosave, and is not in the range
 * of pages statically defined as 'unsaveable', and it isn't part of
 * a free chunk of pages.
 */
static struct page *saveable_page(struct zone *zone, unsigned long pfn)
{
    struct page *page;

    if (!pfn_valid(pfn)) {
        return NULL;
    }

    page = pfn_to_online_page(pfn);
    if (!page || page_zone(page) != zone) {
        return NULL;
    }

    BUG_ON(PageHighMem(page));

    if (swsusp_page_is_forbidden(page) || swsusp_page_is_free(page)) {
        return NULL;
    }

    if (PageOffline(page)) {
        return NULL;
    }

    if (PageReserved(page) && (!kernel_page_present(page) || pfn_is_nosave(pfn))) {
        return NULL;
    }

    if (page_is_guard(page)) {
        return NULL;
    }

    return page;
}

/**
 * count_data_pages - Compute the total number of saveable non-highmem pages.
 */
static unsigned int count_data_pages(void)
{
    struct zone *zone;
    unsigned long pfn, max_zone_pfn;
    unsigned int n = 0;

    for_each_populated_zone(zone)
    {
        if (is_highmem(zone)) {
            continue;
        }

        mark_free_pages(zone);
        max_zone_pfn = zone_end_pfn(zone);
        for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
            if (saveable_page(zone, pfn)) {
                n++;
            }
        }
    }
    return n;
}

/*
 * This is needed, because copy_page and memcpy are not usable for copying
 * task structs.
 */
static inline void do_copy_page(long *dst, long *src)
{
    int n;

    for (n = PAGE_SIZE / sizeof(long); n; n--) {
        *dst++ = *src++;
    }
}

/**
 * safe_copy_page - Copy a page in a safe way.
 *
 * Check if the page we are going to copy is marked as present in the kernel
 * page tables. This always is the case if CONFIG_DEBUG_PAGEALLOC or
 * CONFIG_ARCH_HAS_SET_DIRECT_MAP is not set. In that case kernel_page_present()
 * always returns 'true'.
 */
static void safe_copy_page(void *dst, struct page *s_page)
{
    if (kernel_page_present(s_page)) {
        do_copy_page(dst, page_address(s_page));
    } else {
        kernel_map_pages(s_page, 1, 1);
        do_copy_page(dst, page_address(s_page));
        kernel_map_pages(s_page, 1, 0);
    }
}

#ifdef CONFIG_HIGHMEM
static inline struct page *page_is_saveable(struct zone *zone, unsigned long pfn)
{
    return is_highmem(zone) ? saveable_highmem_page(zone, pfn) : saveable_page(zone, pfn);
}

static void copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
{
    struct page *s_page, *d_page;
    void *src, *dst;

    s_page = pfn_to_page(src_pfn);
    d_page = pfn_to_page(dst_pfn);
    if (PageHighMem(s_page)) {
        src = kmap_atomic(s_page);
        dst = kmap_atomic(d_page);
        do_copy_page(dst, src);
        kunmap_atomic(dst);
        kunmap_atomic(src);
    } else {
        if (PageHighMem(d_page)) {
            /*
             * The page pointed to by src may contain some kernel
             * data modified by kmap_atomic()
             */
            safe_copy_page(buffer, s_page);
            dst = kmap_atomic(d_page);
            copy_page(dst, buffer);
            kunmap_atomic(dst);
        } else {
            safe_copy_page(page_address(d_page), s_page);
        }
    }
}
#else
#define page_is_saveable(zone, pfn) saveable_page(zone, pfn)

static inline void copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
{
    safe_copy_page(page_address(pfn_to_page(dst_pfn)), pfn_to_page(src_pfn));
}
#endif /* CONFIG_HIGHMEM */

static void copy_data_pages(struct memory_bitmap *copy_bm, struct memory_bitmap *orig_bm)
{
    struct zone *zone;
    unsigned long pfn;

    for_each_populated_zone(zone)
    {
        unsigned long max_zone_pfn;

        mark_free_pages(zone);
        max_zone_pfn = zone_end_pfn(zone);
        for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
            if (page_is_saveable(zone, pfn)) {
                memory_bm_set_bit(orig_bm, pfn);
            }
        }
    }
    memory_bm_position_reset(orig_bm);
    memory_bm_position_reset(copy_bm);
    for (;;) {
        pfn = memory_bm_next_pfn(orig_bm);
        if (unlikely(pfn == BM_END_OF_MAP)) {
            break;
        }
        copy_data_page(memory_bm_next_pfn(copy_bm), pfn);
    }
}

/* Total number of image pages */
static unsigned int nr_copy_pages;
/* Number of pages needed for saving the original pfns of the image pages */
static unsigned int nr_meta_pages;
/*
 * Numbers of normal and highmem page frames allocated for hibernation image
 * before suspending devices.
 */
static unsigned int alloc_normal, alloc_highmem;
/*
 * Memory bitmap used for marking saveable pages (during hibernation) or
 * hibernation image pages (during restore)
 */
static struct memory_bitmap orig_bm;
/*
 * Memory bitmap used during hibernation for marking allocated page frames that
 * will contain copies of saveable pages.  During restore it is initially used
 * for marking hibernation image pages, but then the set bits from it are
 * duplicated in @orig_bm and it is released.  On highmem systems it is next
 * used for marking "safe" highmem pages, but it has to be reinitialized for
 * this purpose.
 */
static struct memory_bitmap copy_bm;

/**
 * swsusp_free - Free pages allocated for hibernation image.
 *
 * Image pages are alocated before snapshot creation, so they need to be
 * released after resume.
 */
void swsusp_free(void)
{
    unsigned long fb_pfn, fr_pfn;

    if (!forbidden_pages_map || !free_pages_map) {
        goto out;
    }

    memory_bm_position_reset(forbidden_pages_map);
    memory_bm_position_reset(free_pages_map);

    while (1) {
        fr_pfn = memory_bm_next_pfn(free_pages_map);
        fb_pfn = memory_bm_next_pfn(forbidden_pages_map);

        /*
         * Find the next bit set in both bitmaps. This is guaranteed to
         * terminate when fb_pfn == fr_pfn == BM_END_OF_MAP.
         */
        do {
            if (fb_pfn < fr_pfn) {
                fb_pfn = memory_bm_next_pfn(forbidden_pages_map);
            }
            if (fr_pfn < fb_pfn) {
                fr_pfn = memory_bm_next_pfn(free_pages_map);
            }
        } while (fb_pfn != fr_pfn);

        if (fr_pfn != BM_END_OF_MAP && pfn_valid(fr_pfn)) {
            struct page *page = pfn_to_page(fr_pfn);

            memory_bm_clear_current(forbidden_pages_map);
            memory_bm_clear_current(free_pages_map);
            hibernate_restore_unprotect_page(page_address(page));
            __free_page(page);
            continue;
        }
        break;
    }

out:
    nr_copy_pages = 0;
    nr_meta_pages = 0;
    restore_pblist = NULL;
    buffer = NULL;
    alloc_normal = 0;
    alloc_highmem = 0;
    hibernate_restore_protection_end();
}

/* Helper functions used for the shrinking of memory. */

#define GFP_IMAGE (GFP_KERNEL | __GFP_NOWARN)

/**
 * preallocate_image_pages - Allocate a number of pages for hibernation image.
 * @nr_pages: Number of page frames to allocate.
 * @mask: GFP flags to use for the allocation.
 *
 * Return value: Number of page frames actually allocated
 */
static unsigned long preallocate_image_pages(unsigned long nr_pages, gfp_t mask)
{
    unsigned long nr_alloc = 0;

    while (nr_pages > 0) {
        struct page *page;

        page = alloc_image_page(mask);
        if (!page) {
            break;
        }
        memory_bm_set_bit(&copy_bm, page_to_pfn(page));
        if (PageHighMem(page)) {
            alloc_highmem++;
        } else {
            alloc_normal++;
        }
        nr_pages--;
        nr_alloc++;
    }

    return nr_alloc;
}

static unsigned long preallocate_image_memory(unsigned long nr_pages, unsigned long avail_normal)
{
    unsigned long alloc;

    if (avail_normal <= alloc_normal) {
        return 0;
    }

    alloc = avail_normal - alloc_normal;
    if (nr_pages < alloc) {
        alloc = nr_pages;
    }

    return preallocate_image_pages(alloc, GFP_IMAGE);
}

#ifdef CONFIG_HIGHMEM
static unsigned long preallocate_image_highmem(unsigned long nr_pages)
{
    return preallocate_image_pages(nr_pages, GFP_IMAGE | __GFP_HIGHMEM);
}

/**
 *  _fraction - Compute (an approximation of) x * (multiplier / base).
 */
static unsigned long _fraction(u64 x, u64 multiplier, u64 base)
{
    return div64_u64(x * multiplier, base);
}

static unsigned long preallocate_highmem_fraction(unsigned long nr_pages, unsigned long highmem, unsigned long total)
{
    unsigned long alloc = _fraction(nr_pages, highmem, total);

    return preallocate_image_pages(alloc, GFP_IMAGE | __GFP_HIGHMEM);
}
#else  /* CONFIG_HIGHMEM */
static inline unsigned long preallocate_image_highmem(unsigned long nr_pages)
{
    return 0;
}

static inline unsigned long preallocate_highmem_fraction(unsigned long nr_pages, unsigned long highmem,
                                                         unsigned long total)
{
    return 0;
}
#endif /* CONFIG_HIGHMEM */

/**
 * free_unnecessary_pages - Release preallocated pages not needed for the image.
 */
static unsigned long free_unnecessary_pages(void)
{
    unsigned long save, to_free_normal, to_free_highmem, free;

    save = count_data_pages();
    if (alloc_normal >= save) {
        to_free_normal = alloc_normal - save;
        save = 0;
    } else {
        to_free_normal = 0;
        save -= alloc_normal;
    }
    save += count_highmem_pages();
    if (alloc_highmem >= save) {
        to_free_highmem = alloc_highmem - save;
    } else {
        to_free_highmem = 0;
        save -= alloc_highmem;
        if (to_free_normal > save) {
            to_free_normal -= save;
        } else {
            to_free_normal = 0;
        }
    }
    free = to_free_normal + to_free_highmem;

    memory_bm_position_reset(&copy_bm);

    while (to_free_normal > 0 || to_free_highmem > 0) {
        unsigned long pfn = memory_bm_next_pfn(&copy_bm);
        struct page *page = pfn_to_page(pfn);

        if (PageHighMem(page)) {
            if (!to_free_highmem) {
                continue;
            }
            to_free_highmem--;
            alloc_highmem--;
        } else {
            if (!to_free_normal) {
                continue;
            }
            to_free_normal--;
            alloc_normal--;
        }
        memory_bm_clear_bit(&copy_bm, pfn);
        swsusp_unset_page_forbidden(page);
        swsusp_unset_page_free(page);
        __free_page(page);
    }

    return free;
}

/**
 * minimum_image_size - Estimate the minimum acceptable size of an image.
 * @saveable: Number of saveable pages in the system.
 *
 * We want to avoid attempting to free too much memory too hard, so estimate the
 * minimum acceptable size of a hibernation image to use as the lower limit for
 * preallocating memory.
 *
 * We assume that the minimum image size should be proportional to
 *
 * [number of saveable pages] - [number of pages that can be freed in theory]
 *
 * where the second term is the sum of (1) reclaimable slab pages, (2) active
 * and (3) inactive anonymous pages, (4) active and (5) inactive file pages.
 */
static unsigned long minimum_image_size(unsigned long saveable)
{
    unsigned long size;

    size = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B) + global_node_page_state(NR_ACTIVE_ANON) +
           global_node_page_state(NR_INACTIVE_ANON) + global_node_page_state(NR_ACTIVE_FILE) +
           global_node_page_state(NR_INACTIVE_FILE);

    return saveable <= size ? 0 : saveable - size;
}

/**
 * hibernate_preallocate_memory - Preallocate memory for hibernation image.
 *
 * To create a hibernation image it is necessary to make a copy of every page
 * frame in use.  We also need a number of page frames to be free during
 * hibernation for allocations made while saving the image and for device
 * drivers, in case they need to allocate memory from their hibernation
 * callbacks (these two numbers are given by PAGES_FOR_IO (which is a rough
 * estimate) and reserved_size divided by PAGE_SIZE (which is tunable through
 * /sys/power/reserved_size, respectively).  To make this happen, we compute the
 * total number of available page frames and allocate at least
 *
 * ([page frames total] + PAGES_FOR_IO + [metadata pages]) / 2
 *  + 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE)
 *
 * of them, which corresponds to the maximum size of a hibernation image.
 *
 * If image_size is set below the number following from the above formula,
 * the preallocation of memory is continued until the total number of saveable
 * pages in the system is below the requested image size or the minimum
 * acceptable image size returned by minimum_image_size(), whichever is greater.
 */
int hibernate_preallocate_memory(void)
{
    struct zone *zone;
    unsigned long saveable, size, max_size, count, highmem, pages = 0;
    unsigned long alloc, save_highmem, pages_highmem, avail_normal;
    ktime_t start, stop;
    int error;

    pr_info("Preallocating image memory\n");
    start = ktime_get();

    error = memory_bm_create(&orig_bm, GFP_IMAGE, PG_ANY);
    if (error) {
        pr_err("Cannot allocate original bitmap\n");
        goto err_out;
    }

    error = memory_bm_create(&copy_bm, GFP_IMAGE, PG_ANY);
    if (error) {
        pr_err("Cannot allocate copy bitmap\n");
        goto err_out;
    }

    alloc_normal = 0;
    alloc_highmem = 0;

    /* Count the number of saveable data pages. */
    save_highmem = count_highmem_pages();
    saveable = count_data_pages();

    /*
     * Compute the total number of page frames we can use (count) and the
     * number of pages needed for image metadata (size).
     */
    count = saveable;
    saveable += save_highmem;
    highmem = save_highmem;
    size = 0;
    for_each_populated_zone(zone)
    {
        size += snapshot_additional_pages(zone);
        if (is_highmem(zone)) {
            highmem += zone_page_state(zone, NR_FREE_PAGES);
        } else {
            count += zone_page_state(zone, NR_FREE_PAGES);
        }
    }
    avail_normal = count;
    count += highmem;
    count -= totalreserve_pages;

    /* Compute the maximum number of saveable pages to leave in memory. */
    max_size = (count - (size + PAGES_FOR_IO)) / SNAPSHOT_TWO - SNAPSHOT_TWO * DIV_ROUND_UP(reserved_size, PAGE_SIZE);
    /* Compute the desired number of image pages specified by image_size. */
    size = DIV_ROUND_UP(image_size, PAGE_SIZE);
    if (size > max_size) {
        size = max_size;
    }
    /*
     * If the desired number of image pages is at least as large as the
     * current number of saveable pages in memory, allocate page frames for
     * the image and we're done.
     */
    if (size >= saveable) {
        pages = preallocate_image_highmem(save_highmem);
        pages += preallocate_image_memory(saveable - pages, avail_normal);
        goto out;
    }

    /* Estimate the minimum size of the image. */
    pages = minimum_image_size(saveable);
    /*
     * To avoid excessive pressure on the normal zone, leave room in it to
     * accommodate an image of the minimum size (unless it's already too
     * small, in which case don't preallocate pages from it at all).
     */
    if (avail_normal > pages) {
        avail_normal -= pages;
    } else {
        avail_normal = 0;
    }
    if (size < pages) {
        size = min_t(unsigned long, pages, max_size);
    }

    /*
     * Let the memory management subsystem know that we're going to need a
     * large number of page frames to allocate and make it free some memory.
     * NOTE: If this is not done, performance will be hurt badly in some
     * test cases.
     */
    shrink_all_memory(saveable - size);

    /*
     * The number of saveable pages in memory was too high, so apply some
     * pressure to decrease it.  First, make room for the largest possible
     * image and fail if that doesn't work.  Next, try to decrease the size
     * of the image as much as indicated by 'size' using allocations from
     * highmem and non-highmem zones separately.
     */
    pages_highmem = preallocate_image_highmem(highmem / SNAPSHOT_TWO);
    alloc = count - max_size;
    if (alloc > pages_highmem) {
        alloc -= pages_highmem;
    } else {
        alloc = 0;
    }
    pages = preallocate_image_memory(alloc, avail_normal);
    if (pages < alloc) {
        /* We have exhausted non-highmem pages, try highmem. */
        alloc -= pages;
        pages += pages_highmem;
        pages_highmem = preallocate_image_highmem(alloc);
        if (pages_highmem < alloc) {
            pr_err("Image allocation is %lu pages short\n", alloc - pages_highmem);
            goto err_out;
        }
        pages += pages_highmem;
        /*
         * size is the desired number of saveable pages to leave in
         * memory, so try to preallocate (all memory - size) pages.
         */
        alloc = (count - pages) - size;
        pages += preallocate_image_highmem(alloc);
    } else {
        /*
         * There are approximately max_size saveable pages at this point
         * and we want to reduce this number down to size.
         */
        alloc = max_size - size;
        size = preallocate_highmem_fraction(alloc, highmem, count);
        pages_highmem += size;
        alloc -= size;
        size = preallocate_image_memory(alloc, avail_normal);
        pages_highmem += preallocate_image_highmem(alloc - size);
        pages += pages_highmem + size;
    }

    /*
     * We only need as many page frames for the image as there are saveable
     * pages in memory, but we have allocated more.  Release the excessive
     * ones now.
     */
    pages -= free_unnecessary_pages();

out:
    stop = ktime_get();
    pr_info("Allocated %lu pages for snapshot\n", pages);
    swsusp_show_speed(start, stop, pages, "Allocated");

    return 0;

err_out:
    swsusp_free();
    return -ENOMEM;
}

#ifdef CONFIG_HIGHMEM
/**
 * count_pages_for_highmem - Count non-highmem pages needed for copying highmem.
 *
 * Compute the number of non-highmem pages that will be necessary for creating
 * copies of highmem pages.
 */
static unsigned int count_pages_for_highmem(unsigned int nr_highmem)
{
    unsigned int free_highmem = count_free_highmem_pages() + alloc_highmem;
    if (free_highmem >= nr_highmem) {
        nr_highmem = 0;
    } else {
        nr_highmem -= free_highmem;
    }

    return nr_highmem;
}
#else
static unsigned int count_pages_for_highmem(unsigned int nr_highmem)
{
    return 0;
}
#endif /* CONFIG_HIGHMEM */

/**
 * enough_free_mem - Check if there is enough free memory for the image.
 */
static int enough_free_mem(unsigned int nr_pages, unsigned int nr_highmem)
{
    struct zone *zone;
    unsigned int free = alloc_normal;

    for_each_populated_zone(zone) if (!is_highmem(zone)) free += zone_page_state(zone, NR_FREE_PAGES);

    nr_pages += count_pages_for_highmem(nr_highmem);
    pr_debug("Normal pages needed: %u + %u, available pages: %u\n", nr_pages, PAGES_FOR_IO, free);

    return free > nr_pages + PAGES_FOR_IO;
}

#ifdef CONFIG_HIGHMEM
/**
 * get_highmem_buffer - Allocate a buffer for highmem pages.
 *
 * If there are some highmem pages in the hibernation image, we may need a
 * buffer to copy them and/or load their data.
 */
static inline int get_highmem_buffer(int safe_needed)
{
    buffer = get_image_page(GFP_ATOMIC, safe_needed);
    return buffer ? 0 : -ENOMEM;
}

/**
 * alloc_highmem_image_pages - Allocate some highmem pages for the image.
 *
 * Try to allocate as many pages as needed, but if the number of free highmem
 * pages is less than that, allocate them all.
 */
static inline unsigned int alloc_highmem_pages(struct memory_bitmap *bm, unsigned int nr_highmem)
{
    unsigned int to_alloc = count_free_highmem_pages();
    if (to_alloc > nr_highmem) {
        to_alloc = nr_highmem;
    }

    nr_highmem -= to_alloc;
    while (to_alloc-- > 0) {
        struct page *page;

        page = alloc_image_page(__GFP_HIGHMEM | __GFP_KSWAPD_RECLAIM);
        memory_bm_set_bit(bm, page_to_pfn(page));
    }
    return nr_highmem;
}
#else
static inline int get_highmem_buffer(int safe_needed)
{
    return 0;
}

static inline unsigned int alloc_highmem_pages(struct memory_bitmap *bm, unsigned int n)
{
    return 0;
}
#endif /* CONFIG_HIGHMEM */

/**
 * swsusp_alloc - Allocate memory for hibernation image.
 *
 * We first try to allocate as many highmem pages as there are
 * saveable highmem pages in the system.  If that fails, we allocate
 * non-highmem pages for the copies of the remaining highmem ones.
 *
 * In this approach it is likely that the copies of highmem pages will
 * also be located in the high memory, because of the way in which
 * copy_data_pages() works.
 */
static int swsusp_alloc(struct memory_bitmap *copy_bm_ex, unsigned int nr_pages, unsigned int nr_highmem)
{
    if (nr_highmem > 0) {
        if (get_highmem_buffer(PG_ANY)) {
            goto err_out;
        }
        if (nr_highmem > alloc_highmem) {
            nr_highmem -= alloc_highmem;
            nr_pages += alloc_highmem_pages(copy_bm_ex, nr_highmem);
        }
    }
    if (nr_pages > alloc_normal) {
        nr_pages -= alloc_normal;
        while (nr_pages-- > 0) {
            struct page *page;

            page = alloc_image_page(GFP_ATOMIC);
            if (!page) {
                goto err_out;
            }
            memory_bm_set_bit(copy_bm_ex, page_to_pfn(page));
        }
    }

    return 0;

err_out:
    swsusp_free();
    return -ENOMEM;
}

asmlinkage __visible int swsusp_save(void)
{
    unsigned int nr_pages, nr_highmem;

    pr_info("Creating image:\n");

    drain_local_pages(NULL);
    nr_pages = count_data_pages();
    nr_highmem = count_highmem_pages();
    pr_info("Need to copy %u pages\n", nr_pages + nr_highmem);

    if (!enough_free_mem(nr_pages, nr_highmem)) {
        pr_err("Not enough free memory\n");
        return -ENOMEM;
    }

    if (swsusp_alloc(&copy_bm, nr_pages, nr_highmem)) {
        pr_err("Memory allocation failed\n");
        return -ENOMEM;
    }

    /*
     * During allocating of suspend pagedir, new cold pages may appear.
     * Kill them.
     */
    drain_local_pages(NULL);
    copy_data_pages(&copy_bm, &orig_bm);

    /*
     * End of critical section. From now on, we can write to memory,
     * but we should not touch disk. This specially means we must _not_
     * touch swap space! Except we must write out our image of course.
     */

    nr_pages += nr_highmem;
    nr_copy_pages = nr_pages;
    nr_meta_pages = DIV_ROUND_UP(nr_pages * sizeof(long), PAGE_SIZE);

    pr_info("Image created (%d pages copied)\n", nr_pages);

    return 0;
}

#ifndef CONFIG_ARCH_HIBERNATION_HEADER
static int init_header_complete(struct swsusp_info *info)
{
    memcpy(&info->uts, init_utsname(), sizeof(struct new_utsname));
    info->version_code = LINUX_VERSION_CODE;
    return 0;
}

static const char *check_image_kernel(struct swsusp_info *info)
{
    if (info->version_code != LINUX_VERSION_CODE) {
        return "kernel version";
    }
    if (strcmp(info->uts.sysname, init_utsname()->sysname)) {
        return "system type";
    }
    if (strcmp(info->uts.release, init_utsname()->release)) {
        return "kernel release";
    }
    if (strcmp(info->uts.version, init_utsname()->version)) {
        return "version";
    }
    if (strcmp(info->uts.machine, init_utsname()->machine)) {
        return "machine";
    }
    return NULL;
}
#endif /* CONFIG_ARCH_HIBERNATION_HEADER */

unsigned long snapshot_get_image_size(void)
{
    return nr_copy_pages + nr_meta_pages + 1;
}

static int init_header(struct swsusp_info *info)
{
    memset(info, 0, sizeof(struct swsusp_info));
    info->num_physpages = get_num_physpages();
    info->image_pages = nr_copy_pages;
    info->pages = snapshot_get_image_size();
    info->size = info->pages;
    info->size <<= PAGE_SHIFT;
    return init_header_complete(info);
}

/**
 * pack_pfns - Prepare PFNs for saving.
 * @bm: Memory bitmap.
 * @buf: Memory buffer to store the PFNs in.
 *
 * PFNs corresponding to set bits in @bm are stored in the area of memory
 * pointed to by @buf (1 page at a time).
 */
static inline void pack_pfns(unsigned long *buf, struct memory_bitmap *bm)
{
    int j;

    for (j = 0; j < PAGE_SIZE / sizeof(long); j++) {
        buf[j] = memory_bm_next_pfn(bm);
        if (unlikely(buf[j] == BM_END_OF_MAP)) {
            break;
        }
    }
}

/**
 * snapshot_read_next - Get the address to read the next image page from.
 * @handle: Snapshot handle to be used for the reading.
 *
 * On the first call, @handle should point to a zeroed snapshot_handle
 * structure.  The structure gets populated then and a pointer to it should be
 * passed to this function every next time.
 *
 * On success, the function returns a positive number.  Then, the caller
 * is allowed to read up to the returned number of bytes from the memory
 * location computed by the data_of() macro.
 *
 * The function returns 0 to indicate the end of the data stream condition,
 * and negative numbers are returned on errors.  If that happens, the structure
 * pointed to by @handle is not updated and should not be used any more.
 */
int snapshot_read_next(struct snapshot_handle *handle)
{
    if (handle->cur > nr_meta_pages + nr_copy_pages) {
        return 0;
    }

    if (!buffer) {
        /* This makes the buffer be freed by swsusp_free() */
        buffer = get_image_page(GFP_ATOMIC, PG_ANY);
        if (!buffer) {
            return -ENOMEM;
        }
    }
    if (!handle->cur) {
        int error;

        error = init_header((struct swsusp_info *)buffer);
        if (error) {
            return error;
        }
        handle->buffer = buffer;
        memory_bm_position_reset(&orig_bm);
        memory_bm_position_reset(&copy_bm);
    } else if (handle->cur <= nr_meta_pages) {
        clear_page(buffer);
        pack_pfns(buffer, &orig_bm);
    } else {
        struct page *page;

        page = pfn_to_page(memory_bm_next_pfn(&copy_bm));
        if (PageHighMem(page)) {
            /*
             * Highmem pages are copied to the buffer,
             * because we can't return with a kmapped
             * highmem page (we may not be called again).
             */
            void *kaddr;

            kaddr = kmap_atomic(page);
            copy_page(buffer, kaddr);
            kunmap_atomic(kaddr);
            handle->buffer = buffer;
        } else {
            handle->buffer = page_address(page);
        }
    }
    handle->cur++;
    return PAGE_SIZE;
}

static void duplicate_memory_bitmap(struct memory_bitmap *dst, struct memory_bitmap *src)
{
    unsigned long pfn;

    memory_bm_position_reset(src);
    pfn = memory_bm_next_pfn(src);
    while (pfn != BM_END_OF_MAP) {
        memory_bm_set_bit(dst, pfn);
        pfn = memory_bm_next_pfn(src);
    }
}

/**
 * mark_unsafe_pages - Mark pages that were used before hibernation.
 *
 * Mark the pages that cannot be used for storing the image during restoration,
 * because they conflict with the pages that had been used before hibernation.
 */
static void mark_unsafe_pages(struct memory_bitmap *bm)
{
    unsigned long pfn;

    /* Clear the "free"/"unsafe" bit for all PFNs */
    memory_bm_position_reset(free_pages_map);
    pfn = memory_bm_next_pfn(free_pages_map);
    while (pfn != BM_END_OF_MAP) {
        memory_bm_clear_current(free_pages_map);
        pfn = memory_bm_next_pfn(free_pages_map);
    }

    /* Mark pages that correspond to the "original" PFNs as "unsafe" */
    duplicate_memory_bitmap(free_pages_map, bm);

    allocated_unsafe_pages = 0;
}

static int check_header(struct swsusp_info *info)
{
    const char *reason;

    reason = check_image_kernel(info);
    if (!reason && info->num_physpages != get_num_physpages()) {
        reason = "memory size";
    }
    if (reason) {
        pr_err("Image mismatch: %s\n", reason);
        return -EPERM;
    }
    return 0;
}

/**
 * load header - Check the image header and copy the data from it.
 */
static int load_header(struct swsusp_info *info)
{
    int error;

    restore_pblist = NULL;
    error = check_header(info);
    if (!error) {
        nr_copy_pages = info->image_pages;
        nr_meta_pages = info->pages - info->image_pages - 1;
    }
    return error;
}

/**
 * unpack_orig_pfns - Set bits corresponding to given PFNs in a memory bitmap.
 * @bm: Memory bitmap.
 * @buf: Area of memory containing the PFNs.
 *
 * For each element of the array pointed to by @buf (1 page at a time), set the
 * corresponding bit in @bm.
 */
static int unpack_orig_pfns(unsigned long *buf, struct memory_bitmap *bm)
{
    int j;

    for (j = 0; j < PAGE_SIZE / sizeof(long); j++) {
        if (unlikely(buf[j] == BM_END_OF_MAP)) {
            break;
        }

        if (pfn_valid(buf[j]) && memory_bm_pfn_present(bm, buf[j])) {
            memory_bm_set_bit(bm, buf[j]);
        } else {
            return -EFAULT;
        }
    }

    return 0;
}

#ifdef CONFIG_HIGHMEM
/*
 * struct highmem_pbe is used for creating the list of highmem pages that
 * should be restored atomically during the resume from disk, because the page
 * frames they have occupied before the suspend are in use.
 */
struct highmem_pbe {
    struct page *copy_page; /* data is here now */
    struct page *orig_page; /* data was here before the suspend */
    struct highmem_pbe *next;
};

/*
 * List of highmem PBEs needed for restoring the highmem pages that were
 * allocated before the suspend and included in the suspend image, but have
 * also been allocated by the "resume" kernel, so their contents cannot be
 * written directly to their "original" page frames.
 */
static struct highmem_pbe *highmem_pblist;

/**
 * count_highmem_image_pages - Compute the number of highmem pages in the image.
 * @bm: Memory bitmap.
 *
 * The bits in @bm that correspond to image pages are assumed to be set.
 */
static unsigned int count_highmem_image_pages(struct memory_bitmap *bm)
{
    unsigned long pfn;
    unsigned int cnt = 0;

    memory_bm_position_reset(bm);
    pfn = memory_bm_next_pfn(bm);
    while (pfn != BM_END_OF_MAP) {
        if (PageHighMem(pfn_to_page(pfn))) {
            cnt++;
        }

        pfn = memory_bm_next_pfn(bm);
    }
    return cnt;
}

static unsigned int safe_highmem_pages;

static struct memory_bitmap *safe_highmem_bm;

/**
 * prepare_highmem_image - Allocate memory for loading highmem data from image.
 * @bm: Pointer to an uninitialized memory bitmap structure.
 * @nr_highmem_p: Pointer to the number of highmem image pages.
 *
 * Try to allocate as many highmem pages as there are highmem image pages
 * (@nr_highmem_p points to the variable containing the number of highmem image
 * pages).  The pages that are "safe" (ie. will not be overwritten when the
 * hibernation image is restored entirely) have the corresponding bits set in
 * @bm (it must be unitialized).
 *
 * NOTE: This function should not be called if there are no highmem image pages.
 */
static int prepare_highmem_image(struct memory_bitmap *bm, unsigned int *nr_highmem_p)
{
    unsigned int to_alloc;

    if (memory_bm_create(bm, GFP_ATOMIC, PG_SAFE)) {
        return -ENOMEM;
    }

    if (get_highmem_buffer(PG_SAFE)) {
        return -ENOMEM;
    }

    to_alloc = count_free_highmem_pages();
    if (to_alloc > *nr_highmem_p) {
        to_alloc = *nr_highmem_p;
    } else {
        *nr_highmem_p = to_alloc;
    }

    safe_highmem_pages = 0;
    while (to_alloc-- > 0) {
        struct page *page;

        page = alloc_page(__GFP_HIGHMEM);
        if (!swsusp_page_is_free(page)) {
            /* The page is "safe", set its bit the bitmap */
            memory_bm_set_bit(bm, page_to_pfn(page));
            safe_highmem_pages++;
        }
        /* Mark the page as allocated */
        swsusp_set_page_forbidden(page);
        swsusp_set_page_free(page);
    }
    memory_bm_position_reset(bm);
    safe_highmem_bm = bm;
    return 0;
}

static struct page *last_highmem_page;

/**
 * get_highmem_page_buffer - Prepare a buffer to store a highmem image page.
 *
 * For a given highmem image page get a buffer that suspend_write_next() should
 * return to its caller to write to.
 *
 * If the page is to be saved to its "original" page frame or a copy of
 * the page is to be made in the highmem, @buffer is returned.  Otherwise,
 * the copy of the page is to be made in normal memory, so the address of
 * the copy is returned.
 *
 * If @buffer is returned, the caller of suspend_write_next() will write
 * the page's contents to @buffer, so they will have to be copied to the
 * right location on the next call to suspend_write_next() and it is done
 * with the help of copy_last_highmem_page().  For this purpose, if
 * @buffer is returned, @last_highmem_page is set to the page to which
 * the data will have to be copied from @buffer.
 */
static void *get_highmem_page_buffer(struct page *page, struct chain_allocator *ca)
{
    struct highmem_pbe *pbe;
    void *kaddr;

    if (swsusp_page_is_forbidden(page) && swsusp_page_is_free(page)) {
        /*
         * We have allocated the "original" page frame and we can
         * use it directly to store the loaded page.
         */
        last_highmem_page = page;
        return buffer;
    }
    /*
     * The "original" page frame has not been allocated and we have to
     * use a "safe" page frame to store the loaded page.
     */
    pbe = chain_alloc(ca, sizeof(struct highmem_pbe));
    if (!pbe) {
        swsusp_free();
        return ERR_PTR(-ENOMEM);
    }
    pbe->orig_page = page;
    if (safe_highmem_pages > 0) {
        struct page *tmp;

        /* Copy of the page will be stored in high memory */
        kaddr = buffer;
        tmp = pfn_to_page(memory_bm_next_pfn(safe_highmem_bm));
        safe_highmem_pages--;
        last_highmem_page = tmp;
        pbe->copy_page = tmp;
    } else {
        /* Copy of the page will be stored in normal memory */
        kaddr = safe_pages_list;
        safe_pages_list = safe_pages_list->next;
        pbe->copy_page = virt_to_page(kaddr);
    }
    pbe->next = highmem_pblist;
    highmem_pblist = pbe;
    return kaddr;
}

/**
 * copy_last_highmem_page - Copy most the most recent highmem image page.
 *
 * Copy the contents of a highmem image from @buffer, where the caller of
 * snapshot_write_next() has stored them, to the right location represented by
 * @last_highmem_page .
 */
static void copy_last_highmem_page(void)
{
    if (last_highmem_page) {
        void *dst;

        dst = kmap_atomic(last_highmem_page);
        copy_page(dst, buffer);
        kunmap_atomic(dst);
        last_highmem_page = NULL;
    }
}

static inline int last_highmem_page_copied(void)
{
    return !last_highmem_page;
}

static inline void free_highmem_data(void)
{
    if (safe_highmem_bm) {
        memory_bm_free(safe_highmem_bm, PG_UNSAFE_CLEAR);
    }

    if (buffer) {
        free_image_page(buffer, PG_UNSAFE_CLEAR);
    }
}
#else
static unsigned int count_highmem_image_pages(struct memory_bitmap *bm)
{
    return 0;
}

static inline int prepare_highmem_image(struct memory_bitmap *bm, unsigned int *nr_highmem_p)
{
    return 0;
}

static inline void *get_highmem_page_buffer(struct page *page, struct chain_allocator *ca)
{
    return ERR_PTR(-EINVAL);
}

static inline void copy_last_highmem_page(void)
{
}
static inline int last_highmem_page_copied(void)
{
    return 1;
}
static inline void free_highmem_data(void)
{
}
#endif /* CONFIG_HIGHMEM */

#define PBES_PER_LINKED_PAGE (LINKED_PAGE_DATA_SIZE / sizeof(struct pbe))

/**
 * prepare_image - Make room for loading hibernation image.
 * @new_bm: Unitialized memory bitmap structure.
 * @bm: Memory bitmap with unsafe pages marked.
 *
 * Use @bm to mark the pages that will be overwritten in the process of
 * restoring the system memory state from the suspend image ("unsafe" pages)
 * and allocate memory for the image.
 *
 * The idea is to allocate a new memory bitmap first and then allocate
 * as many pages as needed for image data, but without specifying what those
 * pages will be used for just yet.  Instead, we mark them all as allocated and
 * create a lists of "safe" pages to be used later.  On systems with high
 * memory a list of "safe" highmem pages is created too.
 */
static int prepare_image(struct memory_bitmap *new_bm, struct memory_bitmap *bm)
{
    unsigned int nr_pages, nr_highmem;
    struct linked_page *lp;
    int error;

    /* If there is no highmem, the buffer will not be necessary */
    free_image_page(buffer, PG_UNSAFE_CLEAR);
    buffer = NULL;

    nr_highmem = count_highmem_image_pages(bm);
    mark_unsafe_pages(bm);

    error = memory_bm_create(new_bm, GFP_ATOMIC, PG_SAFE);
    if (error) {
        goto Free;
    }

    duplicate_memory_bitmap(new_bm, bm);
    memory_bm_free(bm, PG_UNSAFE_KEEP);
    if (nr_highmem > 0) {
        error = prepare_highmem_image(bm, &nr_highmem);
        if (error) {
            goto Free;
        }
    }
    /*
     * Reserve some safe pages for potential later use.
     *
     * NOTE: This way we make sure there will be enough safe pages for the
     * chain_alloc() in get_buffer().  It is a bit wasteful, but
     * nr_copy_pages cannot be greater than 50% of the memory anyway.
     *
     * nr_copy_pages cannot be less than allocated_unsafe_pages too.
     */
    nr_pages = nr_copy_pages - nr_highmem - allocated_unsafe_pages;
    nr_pages = DIV_ROUND_UP(nr_pages, PBES_PER_LINKED_PAGE);
    while (nr_pages > 0) {
        lp = get_image_page(GFP_ATOMIC, PG_SAFE);
        if (!lp) {
            error = -ENOMEM;
            goto Free;
        }
        lp->next = safe_pages_list;
        safe_pages_list = lp;
        nr_pages--;
    }
    /* Preallocate memory for the image */
    nr_pages = nr_copy_pages - nr_highmem - allocated_unsafe_pages;
    while (nr_pages > 0) {
        lp = (struct linked_page *)get_zeroed_page(GFP_ATOMIC);
        if (!lp) {
            error = -ENOMEM;
            goto Free;
        }
        if (!swsusp_page_is_free(virt_to_page(lp))) {
            /* The page is "safe", add it to the list */
            lp->next = safe_pages_list;
            safe_pages_list = lp;
        }
        /* Mark the page as allocated */
        swsusp_set_page_forbidden(virt_to_page(lp));
        swsusp_set_page_free(virt_to_page(lp));
        nr_pages--;
    }
    return 0;

Free:
    swsusp_free();
    return error;
}

/**
 * get_buffer - Get the address to store the next image data page.
 *
 * Get the address that snapshot_write_next() should return to its caller to
 * write to.
 */
static void *get_buffer(struct memory_bitmap *bm, struct chain_allocator *ca)
{
    struct pbe *pbe;
    struct page *page;
    unsigned long pfn = memory_bm_next_pfn(bm);
    if (pfn == BM_END_OF_MAP) {
        return ERR_PTR(-EFAULT);
    }

    page = pfn_to_page(pfn);
    if (PageHighMem(page)) {
        return get_highmem_page_buffer(page, ca);
    }

    if (swsusp_page_is_forbidden(page) && swsusp_page_is_free(page)) {
        /*
         * We have allocated the "original" page frame and we can
         * use it directly to store the loaded page.
         */
        return page_address(page);
    }

    /*
     * The "original" page frame has not been allocated and we have to
     * use a "safe" page frame to store the loaded page.
     */
    pbe = chain_alloc(ca, sizeof(struct pbe));
    if (!pbe) {
        swsusp_free();
        return ERR_PTR(-ENOMEM);
    }
    pbe->orig_address = page_address(page);
    pbe->address = safe_pages_list;
    safe_pages_list = safe_pages_list->next;
    pbe->next = restore_pblist;
    restore_pblist = pbe;
    return pbe->address;
}

/**
 * snapshot_write_next - Get the address to store the next image page.
 * @handle: Snapshot handle structure to guide the writing.
 *
 * On the first call, @handle should point to a zeroed snapshot_handle
 * structure.  The structure gets populated then and a pointer to it should be
 * passed to this function every next time.
 *
 * On success, the function returns a positive number.  Then, the caller
 * is allowed to write up to the returned number of bytes to the memory
 * location computed by the data_of() macro.
 *
 * The function returns 0 to indicate the "end of file" condition.  Negative
 * numbers are returned on errors, in which cases the structure pointed to by
 * @handle is not updated and should not be used any more.
 */
int snapshot_write_next(struct snapshot_handle *handle)
{
    static struct chain_allocator ca;
    int error = 0;

    /* Check if we have already loaded the entire image */
    if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages) {
        return 0;
    }

    handle->sync_read = 1;

    if (!handle->cur) {
        if (!buffer) {
            /* This makes the buffer be freed by swsusp_free() */
            buffer = get_image_page(GFP_ATOMIC, PG_ANY);
        }

        if (!buffer) {
            return -ENOMEM;
        }

        handle->buffer = buffer;
    } else if (handle->cur == 1) {
        error = load_header(buffer);
        if (error) {
            return error;
        }

        safe_pages_list = NULL;

        error = memory_bm_create(&copy_bm, GFP_ATOMIC, PG_ANY);
        if (error) {
            return error;
        }

        hibernate_restore_protection_begin();
    } else if (handle->cur <= nr_meta_pages + 1) {
        error = unpack_orig_pfns(buffer, &copy_bm);
        if (error) {
            return error;
        }

        if (handle->cur == nr_meta_pages + 1) {
            error = prepare_image(&orig_bm, &copy_bm);
            if (error) {
                return error;
            }

            chain_init(&ca, GFP_ATOMIC, PG_SAFE);
            memory_bm_position_reset(&orig_bm);
            restore_pblist = NULL;
            handle->buffer = get_buffer(&orig_bm, &ca);
            handle->sync_read = 0;
            if (IS_ERR(handle->buffer)) {
                return PTR_ERR(handle->buffer);
            }
        }
    } else {
        copy_last_highmem_page();
        hibernate_restore_protect_page(handle->buffer);
        handle->buffer = get_buffer(&orig_bm, &ca);
        if (IS_ERR(handle->buffer)) {
            return PTR_ERR(handle->buffer);
        }
        if (handle->buffer != buffer) {
            handle->sync_read = 0;
        }
    }
    handle->cur++;
    return PAGE_SIZE;
}

/**
 * snapshot_write_finalize - Complete the loading of a hibernation image.
 *
 * Must be called after the last call to snapshot_write_next() in case the last
 * page in the image happens to be a highmem page and its contents should be
 * stored in highmem.  Additionally, it recycles bitmap memory that's not
 * necessary any more.
 */
void snapshot_write_finalize(struct snapshot_handle *handle)
{
    copy_last_highmem_page();
    hibernate_restore_protect_page(handle->buffer);
    /* Do that only if we have loaded the image entirely */
    if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages) {
        memory_bm_recycle(&orig_bm);
        free_highmem_data();
    }
}

int snapshot_image_loaded(struct snapshot_handle *handle)
{
    return !(!nr_copy_pages || !last_highmem_page_copied() || handle->cur <= nr_meta_pages + nr_copy_pages);
}

#ifdef CONFIG_HIGHMEM
/* Assumes that @buf is ready and points to a "safe" page */
static inline void swap_two_pages_data(struct page *p1, struct page *p2, void *buf)
{
    void *kaddr1, *kaddr2;

    kaddr1 = kmap_atomic(p1);
    kaddr2 = kmap_atomic(p2);
    copy_page(buf, kaddr1);
    copy_page(kaddr1, kaddr2);
    copy_page(kaddr2, buf);
    kunmap_atomic(kaddr2);
    kunmap_atomic(kaddr1);
}

/**
 * restore_highmem - Put highmem image pages into their original locations.
 *
 * For each highmem page that was in use before hibernation and is included in
 * the image, and also has been allocated by the "restore" kernel, swap its
 * current contents with the previous (ie. "before hibernation") ones.
 *
 * If the restore eventually fails, we can call this function once again and
 * restore the highmem state as seen by the restore kernel.
 */
int restore_highmem(void)
{
    struct highmem_pbe *pbe = highmem_pblist;
    void *buf;

    if (!pbe) {
        return 0;
    }

    buf = get_image_page(GFP_ATOMIC, PG_SAFE);
    if (!buf) {
        return -ENOMEM;
    }

    while (pbe) {
        swap_two_pages_data(pbe->copy_page, pbe->orig_page, buf);
        pbe = pbe->next;
    }
    free_image_page(buf, PG_UNSAFE_CLEAR);
    return 0;
}
#endif /* CONFIG_HIGHMEM */
